Análisis meiótico de una cruza entre girasol cultivado (Helianthus annuus L. var. macrocarpus) y girasol silvestre (Helianthus annuus L. ssp. texanus Heiser)

Abstract

Patterns of meiotic chromosome pairing were compared between three sunflower plants: cultivated sunflower (Helianthus annuus L. var. macrocarpus, public line HA 89), wild sunflower (Helianthus annuus L. ssp. texanus Heiser, collected in Saltillo, Coah.), and the F 1 hybrid. The study was carried out through analysis of meiocytes in diakinesis and metaphase I, based on the meiotic configuration frequency. Pollen viability was evaluated by means of a staining method. Chromosome pairing was normal in the three materials, with absence of univalents and multivalents, and only chain and ring bivalents were observed, therefore the parental genomes are highly compatible in meiosis. The hybrid showed a chromosome pairing index of 0.82, close to the midparent value (0.80), and the differences between the hybrid and each parental taxon (cultivated 0.87, and wild 0.75) were highly significant. Besides, this index was variable within populations. This indicates that the chiasma number is under multigenic control and is affected by the environment. Thus, a population formed with both progenitors could be used to analyze the quantitative trait loci (QTLs) for meiotic chromosome pairing. The pollen viability in the hybrid (92.58%) was similar to that found in the parental taxa (wild 95.57%, and cultivated 95.33%). The pollen viability of the F 1 was high, it showed fertility, and the parental genomes were highly compatible in meiosis, confirming that there is no barrier for the sexual reproduction, and that gene flow and transference of desirables characters from wild to cultivated H. annuus are easily attainable.

Transcriptomic landscape of prophase I sunflower male meiocytes

“…If tetrads or pollen grains were observed, the floral buds were discarded. This protocol is a modification of one previously reported in Rodríguez-de-la Paz et al ( 2007 ). Meiocytes from floral buds that were in prophase I were collected in RNAlater solution (Qiagen, Valencia, CA) and stored at −70°C until RNA extraction.…”

“…Plants were fertilized weekly with the Long Ashton nutrient solution (Phillips and Jennings, 1976 ) until the beginning of the R2 development stage (Schneiter and Miller, 1981 ). At this stage, when the floral buds were around of 2.0 cm in diameter [early meiotic stages, according to our previous observations as well as (Rodríguez-de-la Paz et al, 2007 )] approximately 10 disc florets of the floral bud were harvested and placed on a concave glass slide with 80μL of sterile distilled water, and squashed with dissecting needles to release the meiocytes. Collected meiocytes were observed by microscopy without staining in order to verify that they remained associated with each other, forming the “worm” structure characteristic of meiocytes in prophase I (Yang et al, 2011 ) (see Figure 1 ).…”

“…Whole-genome sequencing of this species is in progress (Kane et al, 2011 ). In addition, the technical feasibility of isolating nearly pure populations of male meiocytes in well-defined stages of meiosis without sophisticated techniques or laboratory equipment (Rodríguez-de-la Paz et al, 2007 ), makes this plant an excellent model for the study of meiotic gene expression. Here we present an RNA-seq transcriptome analysis of male sunflower meiocytes during prophase I, and compare it with a profile of a somatic library of tissues from the same line (HA89).…”